This present invention relates to an improved lead screw type variable resistor which can be connected in a circuit to act as a rheostat or as a potentiometer.
The state of the art in lead screw type variable resistors is exemplified in U.S. Pat. Nos. 2,862,089; 3,124,779; 3,569,897; 3,631,372; 3,732,520; and 3,742,421. In these known variable resistors, five basic elements are required: a rotatably supported lead screw, a resistance element, a slider carried by said lead screw, a first circuit element electrically connected to one end of said lead screw, and a second circuit element electrically connected to said slider. More particularly, U.S. Pat. No. 3,742,421 discloses a potentiometer with a conductive lead screw rotatably carried by a pair of mounts, one of said mounts being connected to a first circuit element. The mounts are fixed to a substrate which carries a resistive element parallel to the lead screw. A conductive slider engages both the lead screw and the resistance element, the slider moving along the resistance element in response to rotation of the lead screw. A second circuit element is connected to one end of the resistance element, and the resistance between the two circuit elements may thus be varied by rotating the lead screw to vary the length of the electrical path through the resistance element. In the very competitive market for variable resistors and potentiometers of this configuration, it is desirable to reduce the number of parts to reduce unit cost.